I don't have the specific information that you refer to, but I wouldn't be surprised if this were the case because Iran's persecution, since I have documented it, appears particularly focused on new converts from Islam to Christianity.
Iran presents to me—and I mean as peace is in effect—that the traditional Christian communities have an easier time than the newer converts. I am not saying that they have equality of status because if you look at the constitution, there is again a gradation there. But I think the persecution in Iran is focused on new converts to Christianity, who aren't defined by their Muslim names and therefore face harassment, persecution, and so on and so forth.
If there were traditional Christian communities coming to Iran, that may well be something that's happening and it's not out of the ordinary.